Implementazione di un client creazione socket connessione Dobbiamo - PDF document

Implementazione di un client creazione socket connessione Dobbiamo andare a costruire un programma scambio dati in C che richiede un servizio chiusura canale socket() socket() SOCK_DGRAM SOCK_STREAM “/etc/protocols” SOCK_RAW SOCK_SEQPACKET Connect() #include <sys/socket.h> read()/write() int s; s = socket (domain, type, protocol) AF_UNIX close() AF_INET AF_NS 1

# # Internet protocols socket() # # $FreeBSD: src/etc/protocols,v 1.13.2.1 2000/09/24 11:26:39 asm odai Exp $ # from: @(#)protocols 5.1 (Berkeley) 4/17/89 ? # # See also http://www.isi.edu/in-notes/iana/assignments/protocol -numbers # ip 0 IP # internet protocol, pseudo protocol number icmp 1 ICMP # internet control message protocol int s; igmp 2 IGMP # internet group management protocol ggp 3 GGP # gateway-gateway protocol s = socket(AF_INET, SOCK_STREAM, 0); ipencap 4 IP-ENCAP # IP encapsulated in IP (officially ``IP'') st2 5 ST2 # ST2 datagram mode (RFC 1819) If ( s < 0 ) { tcp 6 TCP # transmission control protocol cbt 7 CBT # CBT, Tony Ballardie <A.Ballardie@cs.ucl.ac.uk> egp 8 EGP # exterior gateway protocol perror("socket() "); nvp 11 NVP-II # Network Voice Protocol pup 12 PUP # PARC universal packet protocol exit(1); argus 13 ARGUS # ARGUS emcon 14 EMCON # EMCON } xnet 15 XNET # Cross Net Debugger chaos 16 CHAOS # Chaos udp 17 UDP # user datagram protocol ... getprotobyname() int s, protocol_number; struct protoent *protocol_entry; protocol_entry = getprotobyname("tcp"); If ( protocol_entry == NULL ) { perror("getprotobyname() "); exit(1); #include <sys/socket.h> } protocol_number = protocol_entry -> p_proto; struct protoent *p ; s = socket(AF_INET, SOCK_STREAM, protocol_number); if ( s < 0 ) { p = getprotobyname (“name”) perror("socket() "); exit(2); } 2

connect() struct sockaddr_un struct sockaddr_in sizeof(addr) struct sockaddr_un sun_family #include <sys/socket.h> Dominio int error; sun_path error = connect(socket, addr, len); Locazione della socket nel file system socket() struct sockaddr_in hton / ntoh sin_family Host -> network Short (16 bit) htons(int) Dominio Long (32 bit) htonl(int) sin_port Porta (16 bit indirizzo transport) Network - > host sin_addr Short (16 bit) ntohs(int) Indirizzo IP Long (32 bit) ntohl(int) 3

gethostbyname() gethostbyname() struct hostent bcopy() h_addr #include <sys/socket.h> struct in_addr htons(porta) struct hostent *server; server = gethostbyname(“name”); assegnamento struct sockaddr_in struct hosten t *server_host; inet_addr() struct in_addr server_host_addr; struct sockaddr_in server_addr; server_host = gethostbyname(“ www.dsi.unimi.it "); if (!server_host) { perror("gethostbyname() "); exit(1); } #include <sys/socket.h> bcopy(server_host->h_addr, &server_host_addr, server->h_length); unsigned long addr; server_addr.sin_family = AF_INET; server_addr.sin_port = htons(12345); addr = inet_addr(“xxx.xxx.xxx.xxx”); bcopy(&server_host_addr, &server_addr.sin_addr, sizeof(server_host_addr)); if(connect(s, &server_addr, sizeof(server_addr)==-1) { server_addr.sin_addr.s_addr = addr perror("connect() "); exit(1); } 4

getservbyname() struct servent *service_entry; int service_port; Get SERVICE by name service_entry = getservbyname("chargen", "tcp"); if(!service_entry) { perror("getservbyname() "); /etc/services exit(2); } service_port = service_entry.s_port; struct servent *service; service = getservbyname(“service”, proto) # # Network services, Internet style systat 11/tcp users #Active Users # systat 11/udp users #Active Users # daytime 13/tcp # $FreeBSD: src/etc/services,v 1.62.2.3 2000/10/05 07:37:37 daytime 13/udp # sheldonh Exp $ qotd 17/tcp quote #Quote of the Day # From: @(#)services 5.8 (Berkeley) 5/9/91 qotd 17/udp quote #Quote of the Day # chargen 19/tcp ttytst #Character Generator # WELL KNOWN PORT NUMBERS chargen 19/udp ttytst #Character Generator # ftp-data 20/tcp #File Transfer [Default Data] rtmp 1/ddp #Routing Table Maintenance Protocol ftp-data 20/udp #File Transfer [Default Data] tcpmux 1/tcp #TCP Port Service Multiplexer ftp 21/tcp #File Transfer [Control] tcpmux 1/udp #TCP Port Service Multiplexer ftp 21/udp #File Transfer [Control] nbp 2/ddp #Name Binding Protocol ssh 22/tcp #Secure Shell Login echo 4/ddp #AppleTalk Echo Protocol ssh 22/udp #Secure Shell Login echo 7/tcp telnet 23/tcp echo 7/udp telnet 23/udp discard 9/tcp sink null ... discard 9/udp sink null 5

read / write close() int num_bytes; num_bytes = read(socket, buffer, size); int error; error = close(socket); int num_bytes; num_bytes = write(socket, buffer, size); 6